Semantic Illusions and How to Spot Them

How many animals of each kind did Moses take on the ark?

It’s two right?

The answer is none. I’m not trying to start some sort of religious debate here. According to the bible, Moses didn’t build the ark, Noah did.

Maybe you are a theology buff and your sharp eye caught this on the first read through. Maybe you aren’t familiar with the bible story though so it might not have been a fair test. Let’s try another one.

What is the name of the holiday where kids dress up and go out to give candy?

If you answered Halloween, you’d be wrong again. Kids don’t give candy on Halloween, they get candy handed out to them. So what causes our brains to skip over the most important part of the sentence and just decide that “It’s fine, I know the answer to this”?

If you remember last week when we talked about garden path sentences, I mentioned that our brains are driven by efficiency. That desire for maximum efficiency might also be able to explain why these sentences, known to linguists as “Moses illusions”, seem to trip us up. One theory with these Moses illusions is that our brains reach a point in processing these sentences where they feel that they have enough information to answer the question that they can ignore the wrong information.

According to some research out of the University of Maryland this is likely due to what is known as shallow processing. Shallow processing is a bit of a broad term, and the definition of it changes depending on the “thing” that our brains our processing. In garden path sentences for instance, our brains decide what the most likely interpretation of the sentence is before we get to the end of it.

With these Moses illusions, our brains process the sentence to the point where they see key words in the sentence like “holiday”, “dress up”, and “candy”. A word like “give” goes undetected on a quick glance. One reason for this is that our brain feels like it has enough information to answer the question. An even bigger reason though is that “giving” is closely related to “receiving”. If I had given you a sentence like the one below, you likely would not have been fooled as easily.

What is the name of the holiday where kids dress up and go out to grow candy?

Using the word “grow” here might make it easier to catch because it’s such a weird thing that maybe your brain is more likely to catch it. But this might not be fair because our brain has the benefit of hindsight.

Not all Moses illusions are created equal though. You can’t just change out one word in any sentence with something closely related and have it trip people up. It’s not just the similarity of the words that’s causing you to fall for this. The position of the substitution in relation to the other key pieces of information also plays a role in whether people fall for these illusions or not. Sentences with substitutions at the beginning of the sentence are more likely to be noticed by readers than those with subtle substitutions near the end when the brain already has “enough information”.

The explanation that we have at this point in the research is by no means perfect. This is still a growing area of research and there is certainly more to learn about how people read and interpret sentences before we have a definitive answer to why people fall for these. So the next time someone asks you “Which British monarch lit the torch at the London Olympic winter games in 2012?”, you will take a moment to remind them that those were the summer games rather than blindly answering with “Queen Elizabeth”.

Thank you for reading folks! I hope this was informative and interesting to you. If you want to see more of these posts, be sure to follow my Facebook page and get updates when new posts go live. If you have any topics that you want to know more about, please reach out and I will do my best to write about them. In the meantime, remember to speak up and give linguists more data.


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